1. Field of the Invention
The present invention relates generally to a semiconductor package and, more particularly, to coolant path and cooling system for a semiconductor package.
2. Description of the Related Art
Transistors are basic units of integrated circuits forming a semiconductor chip. Over time, semiconductor chip manufactures integrate ever-increasing numbers of transistors in integrated circuits. As the number of the transistors integrated in a semiconductor chip rapidly increases so does the heat generated by the device during operation. Clock speed can also increase heat generated by an operating integrated circuit. Managing heat generated by the operating semiconductor chip has become an important technical issue. Heat may cause permanent damage to the semiconductor chip. As temperature increases chip failure rates increase and limit clock speeds. Consequently, effective dissipation of heat becomes a crucial problem for semiconductor packages.
In a conventional semiconductor package, the heat generated from the semiconductor dissipates externally via its external interface terminals or surfaces of the semiconductor package. For more effective heat dissipation, a heat sink may be attached to a surface of the semiconductor package. For example, in the case of a ball grid array (BGA) package having a plastic resin molding compound encapsulating the semiconductor chip, the heat sink is directly attached to a surface of the molding compound. The molding compound transfers heat energy via conduction to the heat sink and the heat sink dissipates the heat via convection.
Unfortunately, because the plastic resin making up the molding compound has a relatively low thermal conductivity, the efficiency of heat dissipation through the heat sink attached to the surface of the molding compound is similarly low.
To solve this problem, liquid cooling methods have been suggested for circulating a coolant relative to the semiconductor package, as disclosed in U.S. Pat. No. 6,801,429 and Japanese Patent Laid-Open Publication No. 6-61391.
As shown in FIG. 1, a semiconductor package cooling system 10, disclosed in U.S. Pat. No. 6,801,429, comprises a semiconductor package 1 having a coolant path 4 within its molding compound 7. The system 10 dissipates heat generated from a semiconductor chip 2 by circulating a coolant through the coolant path 4 within the molding compound 7.
Both ends of the coolant path 4 are connected to a coolant pipe 8 with a heat exchanger 9 interposed therealong. The coolant circulates by way of a pump 5, operating along the coolant pipe 8 between the heat exchanger 9 and the semiconductor package 1 at the outlet side of the outlet of the coolant path 4.
The semiconductor package 1 is a BGA package, in which the semiconductor chip 2 mounts on the upper surface of a substrate 3 and solder balls 6 protrude from the lower surface of the substrate 3. The portion where the semiconductor chip 2 mounts is protected by the molding compound 7, which is made by encapsulation with liquid plastic resin. The coolant path 4 is formed within the molding compound 7 and above the semiconductor chip 2.
Compared with the prior art heat sink, the semiconductor package cooling system 10 may have higher heat dissipation efficiency. Again, however, because the coolant path 4 is formed within the molding compound 7 having a low thermal conductivity, it may be difficult to cool effectively the semiconductor chip 2.
In addition, the coolant path 4 formed within the molding compound 7 may cause an increase in the overall thickness of the semiconductor package 1, thereby contradicting a general trend towards thinner and smaller semiconductor packaging.
On the other hand, as shown in FIG. 2, a liquid cooled semiconductor package 11, disclosed in Japanese Patent Laid-Open Publication No. 6-61391, is a ceramic package having a base substrate 13, a semiconductor chip 12 mounted on the base substrate 13, and a lid 15 hermetically sealing the base substrate 13 and the semiconductor chip 12. This hermetic seal forms a package body 17. A coolant path 14 passes through the base substrate 13.
By circulating a coolant through the coolant path 14 of the base substrate 13, as attached to the back surface of the semiconductor chip 12, the liquid-cooled semiconductor package 11 may have higher heat dissipation efficiency than the semiconductor package cooling system 10 shown in FIG. 1.
However, the base substrate 13, acting as a heat transfer medium, lying between the coolant path 14 and the semiconductor chip 12, may become an obstacle to effective cooling of the semiconductor chip 12.
In addition, the coolant path 14 formed within the base substrate 13 may cause the base substrate 13 to become thicker, thereby increasing the overall thickness of the semiconductor package 11.
Accordingly, there is a need to form an improved coolant path enabling effective cooling of the semiconductor chip while facilitating the general trend toward smaller integrated circuit packaging.